Shell type outer ring, which can be formed by pressing, have been gaining attention because they are lightweight and can be manufactured inexsensively.
But since a shell-type outer ring is formed from a thin steel plate, it is difficult to rigidly join with a shaft. A weak joint between the outer ring and the shaft could markedly lower the performance of the homokinetic joint.
Unexamined Japanese Patent Publication 58-8831 proposes to join a shell-type outer ring to a shaft by means of bolts or by welding.
But bolting or welding reqiures a step in addition to forming an outer ring by pressing. Since such a completely different manufacturing step must to be carried out in a single manufacturing line, workability tends to be low.
Moreover, in the welding method, the strength of the outer ring tends to drop at its joint due to the influence of welding heat. Also, in situations where welding is not uniform; a high loading torque may break the joint portion between the outer ring and the shaft.
An object of this invention is to provide an arrangement for joining the outer ring of a homokinetic joint to its shaft with high reliability, not by welding, but by a simple mechanical means.
According to this invention, there is provided an arrangement for joining an outer ring to a shaft of a homokinetic joint. The arrangement is comprised of a hole formed in the outer ring to receive the shaft, the hole being formed by pressing. The hole, in turn, has a plurality of flat surfaces or grooves. One end of the shaft is then press-fitted into the hole to join the outer ring to the shaft.
Preferably, the inner surface of the hole is harder than the engaging portion at one end of the shaft.
Since the outer ring and the shaft are prevented from turning relative to each other by the flat surfaces or serrated grooves formed on the inner periphery of the hole of the outer ring in which the shaft is press-fitted, the outer ring and the shaft can be coupled together with high reliability.
Since the surface of the hole formed in the outer ring is harder than the portion of the shaft inserted into the hole, the shaft can be held stably in position once it is press-fitted in the hole, with the portion of the shaft fitted in the hole deformed so as to conform to the shape of the hole.